The present invention provides compositions and methods for decreasing IgE levels and for alleviating allergic symptoms in canines. The compositions comprise chimeric canine anti-IgE mAbs and the methods are useful for treating allergies in canines.
It is estimated that up to 30% of all dogs suffer from allergies or allergy-related skin disorders. Specifically, allergic dermatitis has been estimated to affect between 3% and 15% of the entire canine population. Given the prevalence of allergies in dogs, there is a need to develop methods and compositions to properly diagnose and treat, canine allergies.
The substances most likely to cause an allergic reaction vary from species to species. Common canine allergens include fleas, pollens, molds and dust. Allergy to fleas is believed to be the most common dog allergy. Typically, a flea""s saliva is the allergen, and a single fleabite can cause substantial itching. An additional form of allergy in dogs is termed atopy. Atopy is a condition where a dog. is allergic to inhalants such as pollens, molds or microscopic mites found in house dust. Current treatments of canine allergies often focus on the use of steroids which cause undesirable side effects or allergen-mediated desensitization which requires a different treatment for each type of allergy.
In mammals, antibody molecules are classified into various isotypes referred to as IgA, IgD, IgE, IgG, and IgM. Antibody molecules consist of heavy and light chain components. The heavy chains of molecules of a given isotype have extensive regions of amino acid sequence homology, and conversely have regions of difference from antibodies belonging to other isotypes. The shared regions of the heavy chains provide members of each isotype with common abilities to bind to certain cell surface receptors or to other macromolecules such as complement, and therefore to activate particular immune effector functions. Accordingly, separation of antibody molecules into isotypes also serves to separate the antibodies according to a set of effector functions that they commonly activate. In humans and dogs, Immunoglobulin E (IgE) is involved in allergy, and recognizes antigen in immediate hypersensitivity reactions.
Furthermore, IgE is the antibody type that is understood to be an important mediator of allergic response in mammals, including Type I immediate hypersensitivity. IgE molecules bind to receptors on mediator cells such as mast cells. This binding occurs when the Fc region of the IgE molecule is bound to Fc receptors on the mast cells. When such cell-bound IgE antibodies then bind to an allergen, the allergen cross-links multiple IgE antibodies on the mast cell surface. This cross-linking mediates Type I immediate hypersensitivity reactions and causes release of histamines and other molecules that produce symptoms associated with allergy.
In humans the serum level of total IgE is diagnostic of allergic disease. To explore the possibility that the serum level of IgE might also be diagnostic of allergy in dogs, DeBoer and Hill performed additional studies. (Hill and DeBoer, Am. J. Vet. Res. 55 (7):944-48 (1994)). They used monoclonal antibody (xe2x80x9cmAbxe2x80x9d) D9, in an ELISA assay with the following configuration: D9 was bound to a substrate, antibodies were captured by D9 and then D9 having a marker was used to flag the captured antibody.
The Hill and DeBoer ELISA was used to establish the total amount of IgE in canine serum in an effort to diagnose canine allergy. However, it was found that quantifying IgE was not useful for diagnosing allergy in dogs. (See, e.g., Abstract and Discussion sections of Hill and DeBoer.) This finding was in direct contrast to the situation in human immunology. This result points out the difficulty of any attempt to correlate data between animals of two different genera.
This difficulty is further exemplified by the fact that dogs can be allergic to a different set of antigens than humans are. Allergies to fleas, for instance, are a severe problem for dogs but not humans. Furthermore, in instances where dogs and humans appear to be allergic to the same allergen extract, studies by doctors Esch and Greer of Greer Laboratories (Lenoir, N.C.), have indicated that the specific allergens in an allergen extract which produce canine disease are not necessarily the same allergens that produce disease in humans. For example, it is known that the immunodominant components of dust mite extracts are different in dogs than in humans.
Adding to the difficulty of study across genera of allergic mechanisms and response is that allergies in dogs are primarily expressed in the skin, while humans primarily exhibit allergic symptoms in the respiratory system. Additionally, eosinophilia is correlated to allergies in humans, but not in dogs.
In considering the administration of a therapeutic composition to treat a physiological condition, when recombinant or chimeric molecules are administered in vivo to an animal, they may be quickly cleared from that animal. Recombinant IgG molecules have been used to increase the half-life of recombinant molecules when the recombinants are administered to an animal. E.g., Capon, D., Chamow, S., et al., xe2x80x9cDesigning CD4 immunoadhesins,xe2x80x9d Nature 337:525 (1989); Byrn, R., Mordenti, C., et al., xe2x80x9cBiological Properties of a CD4 Immunoadhesin,xe2x80x9d Nature 344:667 (1990); Haak-Frendscho, M., Ridgway, J., et al., xe2x80x9cHuman IgE Receptor Alpha-Chain IgG Chimera Blocks Passive Cutaneous Anaphylaxis Reaction in vitro,xe2x80x9d Journal of Immunology 151:351-53 (1993); U.S. Pat. No. 5,116,964, issued May 26, 1992 to Capon, D. J., et al. entitled xe2x80x9cHybrid Immunoglobulinsxe2x80x9d.
It is generally accepted that in humans IgG is the immunoglobulin isotype with the longest serum half-life. In dogs, the isotype with the longest half-life is not known. Although the sequences that are believed to correspond to a portion of exon 1 and 3 of at least two and possibly all four heavy chain canine IgG immunoglobulin sequences have been reported in U.S. Pat. No. 5,593,861 to Maeda et al., it is not known which of these heavy chain sequences is part of the IgG structure with the longest half-life in dogs.
IgE levels are elevated in human patients experiencing allergic disease, and IgE is believed to mediate allergic symptoms. Although the levels of serum IgE may not correlate with allergic disease in dogs, it may nevertheless be desirable to decrease IgE levels as a mechanism for alleviating allergic symptoms.
Furthermore, there is a need for compositions and methods for treatment of canine allergies which avoid the disadvantages of the conventional compositions and methods, yet provide effective treatment for canine allergies.
One object of the present invention is to provide compositions and methods for treatment of canine allergies, with substantially less side effects than those experienced with steroid treatments.
Another object of the invention is to provide compositions and methods of treatment for alleviating canine allergy symptoms that are effective independent of the type of allergen, and compositions and methods where treatment is based on the presence of an allergic response rather than a specific allergen.
Another object of the present invention is to provide compositions and methods of treatment for alleviating canine allergy symptoms by targeting IgE synthesis.
These and other objects will be apparent to those skilled in the art from the following disclosure and appended claims.
The present invention concerns compositions and methods for treating allergy in dogs. More particularly, the invention provides methods and compositions for administration to dogs, which compositions actually bind the dog""s immunoglobulin E molecules so that the binding of free, serum IgE will inhibit this IgE from binding to the high affinity IgE receptor on mast cells and basophils. The compositions and methods provided may eliminate or reduce levels of free serum IgE. Lower free serum IgE levels may down regulate the synthesis and expression of the high affinity IgE receptor on basophils and mast cells. The result may be the reduction or elimination of free and/or total serum IgE and the reduction or elimination of the IgE response to allergen on skin mast cells. By xe2x80x9cfree serum IgExe2x80x9d is meant that IgE which is able to bind to the high affinity IgE receptor, and is unbound IgE in serum.
We have demonstrated that sustained elimination of detectable free and/or total serum IgE for 7 days and possibly a shorter time period results in a negative, feedback-loop that continues to suppress IgE synthesis. Sustained suppression of IgE synthesis will result in the elimination of a skin response to allergen.
In a preferred embodiment, the specificity and structure of a chimeric anti-IgE molecule of the present invention may allow for direct targeting of the IgE+ B cell. This binding may result in a reduction or elimination of IgE synthesis either through negative stimulation of the mature B cell or by destruction of the B cell by apoptosis or complement-mediated lysis.
The present invention may therefore comprise an IgE receptor molecule which comprises a chimera and which specifically binds to canine IgE. The receptor molecule may be an antibody molecule, preferably a monoclonal antibody (xe2x80x9cmAbxe2x80x9d), and the mAb may preferably have an affinity for exon 3 of canine IgE. The chimera may comprise canine and mouse immunoglobulin. The chimera may further comprise canine constant heavy and light domains fused to mouse heavy and light chain variable regions. The receptors and antibody molecules of the present invention may also comprise IgG heavy chain sequences.
The receptors and antibody molecules of the present invention may prevent binding of IgE to a second IgE receptor and the second IgE receptor may be located on one or more of a mast cell or basophil. The receptors and antibody molecules of the present invention may be comprised of protein, peptides, or other organic molecules.
The present invention also provides methods of treating canine allergies comprising administering to the canine a receptor or monoclonal antibody which comprises a chimera of the present invention and specifically binds to canine IgE. The methods of the present invention may result in a lowering of serum IgE levels in the treated canine, or in the binding of IgE on B cells and the subsequent elimination of clonal populations of B cells. The methods may also result in binding of serum IgE in plasma, or in an inhibition of IgE production in the treated canine. The lowering of serum IgE levels of the present methods may be caused by a disruption of blocking of interactions between IgE and receptors for IgE which may be located on mast cells or basophils.
The present invention further provides pharmaceutical formulations containing therapeutic amounts of the receptors of the present invention.